weh.. that cable looks so familiar...

by the way. i think it's not good to just use selotape to stick the cable on back of magnet.
try to tie a knob by cable tie.

it shall prevent u pull out the board if u accidentally pull the cable.
if u put like this without a knob on cable. higher chances that when u pull the cable. the electronic board will come out. and snap the both voice coil.
the board is glue with  hold melt glue only (usually) and they are not really super rigid.

to close the hole near the back of the casing. if u feel bass is over tight. try to get some CD cover (those ppl use to put pirated CD). in the middle of the cd bag there's sort of silky paper in middle.

use that to glue it at the holes. and add up multiple layer for fine tune the bass hole porosity. remember the glue shall only apply around the hole, not through out the sheet of paper.

and try put a flat layer of blue tag on the top of the magnet, and not touching the platic part of the place that it holds the magnet.
it might works for this headphone and it might not.
just my 2 cents suggestion . =)